Method and semiconductor component for identifying ambient light fluctuations

Abstract

Fluctuation frequency (F) of an ambient light (S) is identified by: A) specifying first frequency (F 1 ) and second frequency (F 2 ), higher than said first frequency; B) measuring an optical power of the ambient light with a signal receiver ( 2 ) over a measuring time interval (Ti) during a total measuring time (T), which is shorter than or equal to a first cycle duration (P 1 ) belonging to the first frequency; C) detecting the optical power of the ambient light in a time series over the total measuring time; D) determining at least one detection feature for identifying the fluctuation frequency by evaluating the time series; and E) identifying the fluctuation frequency of the ambient light as the first frequency or as the second frequency using the at least one detection feature.

The invention claimed is: 
     
       1. A method for identifying a fluctuation frequency of an ambient light by means of a predetermined first frequency and a predetermined second frequency using a semiconductor component comprising (a) a photodetector to measure an optical power of the ambient light and to generate an electrical signal corresponding to the measured optical power, and (b) a signal processor electrically connected to the photodetector to analyze the electrical signal generated by the photodetector corresponding to the measured optical power over a total measuring time, to determine at least one detection feature in the electrical signal for identifying the fluctuation frequency of the ambient light as the first frequency or as the second frequency, to use the at least one detection feature to identify the fluctuation frequency of the ambient light as the first frequency or as the second frequency, and to output, in an output electrical signal, the identification of the fluctuation frequency, the method comprising the following steps:
 A) specifying the first frequency and the second frequency, the first frequency being lower than the second frequency; 
 B) measuring an optical power of the ambient light using the photodetector over a measuring time interval during the total measuring time, the measuring time interval being equal to a first cycle duration belonging to the first frequency; 
 C) detecting the optical power of the ambient light in a time series over the total measuring time using the photodetector; 
 D) determining, using the signal processor, at least one detection feature for identifying the fluctuation frequency by evaluating the time series, wherein the detection feature is determined from a plurality of period energies which are in each case an optical power integrated up over the measuring time interval; 
 E) identifying, using the signal processor, the fluctuation frequency of the ambient light as the first frequency or as the second frequency by means of the at least one detection feature; and 
 F) outputting by the signal processor, in the output electrical signal, the identification of the fluctuation frequency. 
 
     
     
       2. The method according to  claim 1 , wherein the first frequency differs from the second frequency by at least 10%. 
     
     
       3. The method according to  claim 1 , wherein the first frequency and the second frequency are between inclusively 20 Hz and inclusively 200 Hz, and the measuring time interval is between inclusively 50 ms and inclusively 0.5 ms. 
     
     
       4. The method according to  claim 1 , wherein the first frequency is 100 Hz and the second frequency is 120 Hz. 
     
     
       5. The method according to  claim 1 , wherein the measuring time interval is a cycle duration or a multiple of the cycle duration of the first or of the second frequency and the detection feature is determined from a plurality of period energies, wherein the period energies are in each case an optical power integrated up over the measuring time interval. 
     
     
       6. The method according to  claim 1 , wherein:
 in step D), the detection feature is a time interval between two successive minima of the optical power of the ambient light or a time interval between two successive maxima of the optical power of the ambient light in the time series; and 
 in step E), the fluctuation frequency of the ambient light is identified by a comparison of the time interval with the first cycle duration and a second cycle duration belonging to the second frequency. 
 
     
     
       7. The method according to  claim 6 , wherein:
 in step B), the total measuring time is at least twice as great as the first cycle duration; 
 in step D), a plurality of time intervals is determined in the time series; and 
 in step E) the fluctuation frequency of the ambient light is identified by a comparison of a mean value of the time intervals with the first cycle duration and the second cycle duration. 
 
     
     
       8. The method according to  claim 1 , wherein:
 in step D), the detection feature is a number of the maxima of the optical power or a number of the minima of the optical power in the time series during the total measuring time; and 
 in step E), the fluctuation frequency of the ambient light is identified by a comparison of the number of maxima or the number of minima with a first quotient and a second quotient, wherein the first quotient is a ratio of the total measuring time to the first cycle duration and the second quotient is a ratio of the total measuring time to a second cycle duration belonging to the second frequency. 
 
     
     
       9. The method according to  claim 8 , wherein, in step E), the fluctuation frequency of the ambient light is identified by a comparison of an average of the number of maxima and the number of minima with the first quotient and with the second quotient. 
     
     
       10. The method according to  claim 1 , wherein in step B), at least one of:
 (a) at least three first optical period energies of the ambient light are measured, wherein measuring of the individual first optical period energy is performed in each case over a first measuring time interval which is the first cycle duration; and 
 (b) at least three second optical period energies of the ambient light are measured, wherein measuring the individual second optical period energy is carried out in each case over a second measuring time interval which is a second cycle duration belonging to the second frequency. 
 
     
     
       11. The method according to  claim 10 , wherein:
 in step D), a first absolute energy deviation and a second absolute energy deviation are calculated, wherein the first absolute energy deviation is a difference between a maximum first period energy and a minimum first period energy, and the second absolute energy deviation is a difference between a maximum second period energy and a minimum second period energy; and 
 in step D), the detection feature is a deviation quotient, wherein the deviation quotient is a ratio of the first absolute energy deviation to the second absolute energy deviation. 
 
     
     
       12. The method according to  claim 11 , wherein:
 the first frequency is 100 Hz and the second frequency is 120 Hz; and 
 in step E), for identifying the fluctuation frequency as the first frequency or as the second frequency, the deviation quotient is compared with a reference value of the deviation quotient, wherein the reference value of the deviation quotient is between inclusively 0.5 and inclusively 2.0. 
 
     
     
       13. A semiconductor component for identifying a fluctuation frequency of an ambient light as a predetermined first frequency or as a predetermined second frequency, wherein the semiconductor component comprises:
 a photodetector which measures an optical power of the ambient light and generates an electrical signal corresponding to the measured optical power; 
 a signal processor electrically connected to the photodetector which analyzes the electrical signal generated by the photodetector corresponding to the measured optical power over a total measuring time, determines at least one detection feature in the electrical signal for identifying the fluctuation frequency of the ambient light as the first frequency or as the second frequency, uses the at least one detection feature to identify the fluctuation frequency of the ambient light as the first frequency or as the second frequency and identifies, in an output electrical signal, the fluctuation frequency. 
 
     
     
       14. A display device or mobile electronic device comprising a semiconductor component according to  claim 13 .